Vascular reactivity in the hind limb of the pregnant ewe.

The data generated by this study are consistent with the fact that pregnancy and progesterone treatment are associated with an increase in vascular reactivity to phenylephrine and a decrease in reactivity to angiotensin II in the circulation to the hind limb of the ewe. This shows that the way in which vascular reactivity changes during pregnancy is dependent both upon the circulation and the vasoconstrictor being examined. It suggests that sensitivity and contractility could change in opposite directions in this circulation during pregnancy. This will require additional verification, both as to its existence and whether this is an important normal cardiovascular adaptation to pregnancy.